What will urban rail systems look like in the future?

Railways, with their greater capacity for carrying more people, quickly and with greater energy efficiency, are the best bet to become our mobility backbone. It’s no surprise that some of the most advanced urban rail systems are in places that are already as much as 80% urbanised, such as in Europe.

Of course, engineers’ imaginations have created many alternatives to the original steel-on-steel approach to the railway. Maglev and the much-publicised but so far theoretical Hyperloop are often regarded as the alternatives to watch, but do they really represent the future of rail travel?

Magnetic levitation (maglev) uses powerful magnets to propel the train along dedicated lines that are as straight as possible. The attractive forces between electronically controlled electromagnets in the vehicle and the ferromagnetic guide rails pull the vehicle up, while additional guidance magnets keep it laterally on track. This version of the technology was developed in Germany and is currently used to link Shanghai airport with the city centre at speeds of 267m/h.

However, it’s perhaps Japan that is most associated with maglev. The nation that established the modern era of high-speed trains is also attempting to define the next chapter. Superconducting magnetic levitation (SCMaglev) has been in development for decades but was recently approved to run from Tokyo to Osaka from 2027, when it will complete the 311 mile journey in just over an hour. Unlike the Transrapid system in Shanghai, the Japanese maglev principle uses more powerful superconducting magnets and a guideway design based on repulsive rather than attractive forces.

But while maglev is technically possible, its commercial viability is questionable. There is an extremely high initial infrastructure cost, Japan’s SCMaglev line is expected to cost ¥9tn ($72bn). It also cannot be integrated with existing rail networks and has a phenomenal energy demand, during both construction and operation. This casts serious doubts about maglev’s true potential as an alternative to conventional high-speed technology, which still has enormous potential.

Hyperloop is an elegant idea: travelling seamlessly at 760m/h in gracefully designed pods that arrive as often as every 30 seconds is very appealing. The concept is based around very straight tubes with a partial vacuum applied under the pods. These pods have an electric compressor fan on their nose which actively transfers high-pressure air from the front to the rear, creating an air cushion once a linear electric motor has launched the pod. All of this would be battery and solar powered.

Technically it’s a challenging design, although if someone can make it happen it’s the man who proposed the idea, Elon Musk, the mind behind SpaceX and Tesla. However, Hyperloop is not rail travel. It is, as Mr. Musk puts it, a fifth mode of transport. It’s designed to link Los Angeles to San Francisco, cities hundreds of miles apart that can be connected in an almost straight line over a relative flat landscape. This simply isn’t an option in much of the world.